Method for recovering pyridine bases.



F. E. DODGE & F; H. RHOHES.

METHOD FOR RECOVERING P YRIDINE BASES. APPLICATION FILED JAN. I1. ms.

1 ,274, 998 Patented Aug. 6, 1 918.

am 2 M l the pyridinebases from the saturater ath-l UNITED STATES PATENT QFFICE.

.mmx E. DODGE, or NEW YonK, N; Y. Arm rnnnarcx n. nnonns, or rmnmunrnm, PENNSYLVANIA, ASSIGNORS TO THE ram'r'r COMPANY, A conroaa'rrou or NEW JERSEY.

METHOD FOR RECOVERING PYRIDINEBASES. 1

Specification of Letters Patent.

Patented Aug. o, 1918.

Application filed January 17, 1918. Serial No. 212,875.

To all whom it may concern:

Be it known that we, FRANK E. Donor, of

the city, count and State of. New York,

and Fnnmucx Rnoons, of the city and county of Philadelphia, State of Pennsylvania, both citizens of the United States,

have invented certain new and useful Improvements in Methods for Recovering Pyridine Bases, of which the following is a true and exact description, reference being had to the accompanying drawings, which form a part thereof.

Our invention relates to the recover of liquor of the well ,known direct or semidirect ammonium sulfate processes, and has for its object the economical recovery of the pyridine bases, and incidentally the purification of the bath liquor.

It is well known that in the manufacture of by-product coke and of illuminating gas some pyridine and pyridine homologues (as for example picoline, lutidine, quinoline, etc.,) are formed. A portion of these bases, especially those of the higher boiling points, condense in the hydraulic mains and primary coolers, and are thus contained in the tar. A considerable portion of the lower boiling pyridine bases is, however, not condensed with the tar, but comes through the primary coolers and tar extractors as a component of the gas.

In the direct ammonium sulfate process and in the semi;direct ammonium sulfate rocess the gas from the tar extractors is rced from ammonia by passing through a saturated solution of ammonium sulfate,

which'solution is kept acid with from ten .to sixper cent. of free sulfuric acid. The

ammonia in the gas is absorbed by this acid solution andcrystallizes out from the bath 1 liquor as ammonium sulfate, which is removed and recovered. The pyridine vapor is also absorbed by the solution in'thesat- .urater bath, but only a negligible amount of pyridine or its compounds separates from the bath until the concentration of pyridine"- in the bath reaches a certain minimum value of approximately 2% per cent. The -con-' tamination of the ammonium sulfate by pyridine depends not only on the amount of pyridine in the bath, but also upon the care taken in washing the ammonium salts and with careful washing the bath may be permitted to contain much more pyridine than 21} percent, without loss, of pyridine with the salt.

In our process we remove the bath liquor from a saturater bath which has been in the point where the ammonium sulfate isv contaminated by pyridine sulfates. We then pass ammonia or ammonia vapor into the bath, with the result that the ammonia first reacts with the free acid present to form ammonium sulfate. After most of the free acid is thus neutralized, the ammonia beglns to react with the pyridine sulfate in the solution, forming ammonium sulfate, and setting free the pyridine bases. By saturating the bath solution with ammonia in this way, it is, wehave found, possible to liberate all of the pyridine bases in the bath liquor. Y

Having freed the pyridine bases in the bathliquor from their combination with sulfuric acid as above described, we next proceed to recover the pyridine bases from the tillation may be furnished by the heat of the reaction of the ammonia with the free acid and pyridine sulfate in the solution,

but it is preferable tosupplement this with heat from some outside source.

"The pyridine in .the distillate from the which causes the pyridine bases'to separate as a distinct layer, superimplosed on the layer of water, owing to w ich gravital separation the water and the pyridine bases can be readily drawn oil into separate tanks. It is preferable, but not essential, that .the ammonia or ammonia vapor whichds' caused 'to pass through the bath-liquor in the neutralizing still should be partially dried by passing it through a separator before it a is admitted to the neutralizing still. I

We would also note that in place of using ammonia vapor or ammonia in the neutralizing still, it is possible to use an aqueous solution' of ammonia to neutralize all or a portion of the free acid and of the'pyrid ne sulfate. For example, the aqueous solution of ammonia which is obtained when the distillate is saturated with ammonia gas may be used for this purpose.

We would also note here that an alternative method of recovering the pyridine bases from the neutralized bath liquor containing the pyridine bases freed from combination with the sulfuric acid is to agitate the neutralized solution of the bath with an oil which will take up the pyridine bases. The

oil layer is then separated from the bath and the pyridine bases recovered from it by a suitable means, as for example by agitation with an acid. This particular modification of our process forms the sub ect matter of our co-pending application for Letters Patent filed Jan. 17, l9l8, Ser1al Number 212,376. a

Our invention in its detail will be best understood as described in connection with the apparatus which we have devised for its most efficient practice, and which is shown in the diagrammatic drawing forming part of this application, in which A indicates a storage tank for the bath liquor drawn from the saturater. B is the neutralizing still, which should be lead-lined and into which proper quantities of the old bath liquor is forced from the tank through the pipe C. O is a lead steam 0011 contained in the still, and used for raising the temperature of the bath when necessary. N is a pipe leadin from an ammonia still and as shown, lea ing into the heater and separator M, which is formed with a part1- tion M" and a steam coil M for raising its temperature, M indicating a drain p pe. The dried ammonia passes from the heater and separator through the pipe N to the still, and enters the bath through the cracker pipe indicated at N The still B can be drained through the pipe K, having the valve 70, and leading as shown to a filter L, from a pipe K to thevstorage' tank K P indicates an acid inlet pipe leading into the still B; D isa conduitthrough which the distillates escape from the still B, and which terminates in a worm condenser D located in the condenser tank E and connecting with the pipe D in which is preferably situated a sight glass D having a vent D and Which connects through the pipes D? and D, each provided with valves 01 an'd d, with the receiver tanks E- and E. These tanks are drained at suitable times through the pipes and E at the will of the operator.

ich the liquor passes through the.

age tank H, and through pipe G with the pipe G leading to the tank A, and with the pipe G which may lead to a hot drain tank not shown. g, 9 g and g are valves by which the course of the liquid through and from the pipe G and its connections may be regulated at will. I is a pipe leading from a still or other source of ammonia vapor, and-connecting through the pipes T and I with the receiver tanks E and E, z" and 2' indicating valves. J and J are vents for the ammonia vapor, which of course will be connected with some receptacle for the ammonia.

In operation, the bath liquor is pumped from the tank A into the neutralizing still B, and ammonia, preferably dried in the heater and separator M, is passed through the pipes N and N into the bath, with the result of neutralizin the acid of the bath and decomposing the pyridine sulfat s.

' and the heat of the reaction, supplemented,

if necessary, by extraneous heat, drives ofi" the freed pyridine bases in admixture with watery vapor through the pipe D, the distillate being condensed in the condenser D and E, and the condensed water and yridine bases being delivered into the tan s E monia vapor is then delivered to the receivers E and E through the pipes ll and T with the result that the pyridine bases separate gravitally from the water and the contents of the receivers is then drawn off, the water charged with ammonia b'ein delivered to the tank A or through'the plpe G to a hot drain tank not shown, and the pyridine basesbeing delivered to the tank H.

The apparatus above described forms the subject matter of our co-pending applica tion for Letters Patent filed January 27 1918, Serial Number 212377.

Having now described our invention, what we claim as new and desire to secure by Let'- ters Patent, is: 1. The method of separating the pyridine bases from the saturater baths ofthe direct or semidirect ammonium sulfate processes, which consists in saturating the bath liquor consisting of a saturated acid solution 0 pyridine bases from their combination with the acid of the bath and recovering the freed bath.

2. The method of separating the pyridine bases from the saturater bath of the direct or semi-direct ammonium sulfate processes, which consists in saturating the bath liquor, consisting of a saturated acid solution of ammonium sulfate contaminated with salts' of pyridine, with ammonia to liberate the pyridine bases from the neutralized f pyridine bases from their combination with of pyridine, with ammonia to liberate the the acid of the bath and separating the freepyridine "bases from their combinationwith pyridine bases from the neutralized bath the acid of the bath, separating the freed by distillation. pyridinebases from the neutralized bath by 5 3. The method of separatingthe pyridine distillation, andtreating the condensed dis- 15 bases from the saturater baths of the direct tillate with. ammonia to effect a gravital or semi-direct ammonium sulfate processes, separation of the pyridine bases from the which consists in saturating the bath liquor, condensed liquid. consisting of a saturated acid solution of FRANK E. DODGE.

10 ammonium sufate contaminated with salts FREDRICK H. RHODES. 

